Vinca minor aka Common Periwinkle

Vinca minor is an evergreen ground cover in the dogbane family, Apocynaceae. Gardeners know it as common periwinkle, lesser periwinkle, running myrtle or creeping myrtle. It comes from Europe and western Asia, reaching east to the Caucasus and Turkey. The RHS lists it as native to Britain and Ireland. The genus name comes from a Latin word meaning to bind, after the flexible stems once woven into wreaths.

This is a low, trailing plant that forms a dense mat. Most garden plantings stand 3 to 6 inches (8 to 15 cm) tall. Some sources allow up to 8 inches (20 cm), and the RHS gives an upper limit near 20 inches (0.5 m). A single plant may spread 6 to 18 inches (15 to 45 cm) at first. The stems root wherever they touch the ground, so a patch can cover many feet over time. The thin, wiry stems rise briefly, then arch over and run along the soil. They bleed a milky sap when snapped. The leaves sit in opposite pairs. They are elliptic, glossy dark green, smooth-edged and leathery, about 1 to 2 inches (2.5 to 5 cm) long.

Solitary flowers open in the leaf axils. They are lavender-blue, five-lobed and about 1 inch (2.5 cm) across. The main show comes in spring, from April into June. Scattered blooms often follow through summer and sometimes into autumn. Bumblebees visit the flowers. The fruit is a small brown follicle that few people notice. Named selections offer white, purple or double flowers, plus gold or cream-edged leaves.

Periwinkle grows well in partial or dappled shade and tolerates deep shade. It copes with full sun in cool climates. In hot, sunny spots the leaves tend to yellow and growth suffers. The best soil is moist, fertile and well drained, but the plant adapts to clay, chalk, loam and sand. Once settled, it handles dry soil and shallow, rocky ground. It is hardy in USDA zones 4 to 8, and some sources extend this to zone 3. In the UK it rates H6, hardy across the country.

Gardeners use it to carpet shady ground, to fill in around shrubs and to cover spring bulbs. Its rooting mats hold soil on banks and slopes. Deer tend to leave it alone. Its stems have served in basket making. In herbal medicine, people have used the plant for its alkaloid vincamine.

The chief disease is vinca stem canker, or blight, which can kill large patches. Leaf spot, dieback and rust also occur. Insects rarely cause trouble. The bigger problem is the plant itself. It spreads fast into lawns, beds and wild areas. North Carolina lists it as invasive, and it escapes cultivation in Connecticut. Hard cutting in early spring keeps it in check. The plant has no known food use. Large amounts are poisonous. Pets that eat a lot may suffer vomiting, diarrhoea, low blood pressure, tremors or seizures.